OBJECTIVES: 1. This study extends the investigation of short-term longitudinal methodologies for the study of adult cognitive behavior. Special emphasis is given to the identification of environmental correlates of change in intellectual functions, and the effects of experimental mortality and test-retest effects will be analyzed for successive cohorts and times of measurement. 2. A cross-sectional sample of 500 Ss covering the age range from 22 to 70 years was first studied in 1956 and survivors were retested in 1963, 1970 and 1977. A second sample of 960 Ss was first tested in 1963 and survivors were retested in 1970 and 1977. A third sample of 701 Ss was first tested in 1970 and reexamined in 1977. A new random sample of over 700 Ss was drawn from the same parent population. Measures used include Thurstone's Primary Mental Abilities Test and Schaie's Test of Behavioral Rigidity. In addition, health history, personality and descriptions of individual environments have been collected. 3. Current analyses involve data from the 21-year longitudinal study, the replication of the 14-year longitudinal study and second replication of the seven-year longitudinal study. Also under study are comparisons of the four cross-sectional studies. Effects of experimental mortality and repeated measurement are being assessed for successive cohorts. 4. Joreskog's techniques for comparative factor analysis and linear structural relations analysis (LISREL) will be applied to our data base to investigate structural invariance of factor patterns across age and cohort membership, relations between health, stress and other environmental factors with the maintenance or decline of intellectual ability will be examined.